Research has established that executive functions, the skills required to monitor and control thought and action, are related to achievement in mathematics. Until recently research has focused on working memory, but studies are beginning to show that inhibition skills--the ability to suppress distracting information and unwanted responses--are also important for mathematics. However, these studies employed general mathematics tests and therefore are unable to pinpoint how inhibition skills relate to specific components of mathematics. We explored how inhibition skills are related to overall achievement as well as factual, procedural and conceptual knowledge in 209 participants aged 11-12, 13-14 and adults. General mathematics achievement was more strongly related to inhibition measured in numerical compared with non-numerical contexts. Inhibition skills were related to conceptual knowledge in older participants, but procedural skills in younger participants. These differing relationships can shed light on the mechanisms by which inhibition is involved in mathematics.